Polygonal electric coil



March ,1960 w. VAN- DER HOEK ETAL 2,930,014

POLYGONAL ELECTRIC COIL 2 Sheets-Sheet 1 Filed Dec. 12, 1955 lNVENTORS Ll-EM VAN ER HOEK fix AG NT LEOWRD LOUIS March 22, 1960 w. VAN- DER HOEK ETAL POLYGONAL ELECTRIC COIL 2 Sheets-Sheet 2 Filed Dec. 12, 1955 INVENTORS WILLEM VAN DER HOEK WILHELMUS LEONARD LOUIS LEN AGENT United 2,930,014 POLYGONAL ELECTRIC colL Application December 12, 1955, Serial No. 552,626

Claims priority, application Netherlands December 24, 1954 Claims. (Cl. 336190) This invention relates to electric coils having turns each located substantially in at least one plane at right angles to the axis of the coil.

Such coils (see for example, U.S. Patent No. 1,167,722) have the advantage of a considerably larger copper space factor (copper section divided by winding section) with respect to the conventional coils wound with paper layers between the winding layers and also with respect to coils wound wildly, that is to say irregularly. The copper space factor may be, for example, 80% and more, as compared with at most about 40% in the winding with paper layers. Another advantage is that the winding process may be effected substantially continuously, in contradistinction to the process for the last-mentioned coil in which the winding process must be interrupted after each layer for providing a paper layer. Said advantages are obtained as a result of the fact that the turns of the second layer and of subsequent layers of the coilat least those portions of the turns which are located in the said planes at right angles to the axis of the coil-may be accommodated in the grooves formed between every two adjacent turns of the preceding layer. Perfectly regular Winding without the use of paper layers is thus rendered possible. a

, However, the winding method has the disadvantage of being very critical. If only a single turn assumes a wrong position, the regularity of all subsequent turns is disturbed and the coil cannot be used. Ditficulties are thus involved more particularly for coils having a rectangular aperture, as will be explained more fully hereinafter, even after a comparatively small number of layers, for example layers, has been wound, which difliculties may lead to a considerable reject percentage.

The object of the invention is to provide an embodiment for a coil of the kind concerned having a rectangular window in which said difliculties are avoided. The coil is characterized in that each of the lines on which in each of the end surfaces of the coil the transitions between every two sequential layers are located, exhibits at least one acute bend and extends within a sector of the coil located between two sequential or adjacent half diagonals.

In order that the invention may be readily carried into eflect, it will now be described, by way of example, with reference to the accompanying drawings, in which Figs. 1, 2 and 3, illustrate the known method of winding, the principle of which is also used in the invention.

' Fig. 4 serves to illustrate the difliculties which are involved in winding rectangular coils.

Fig. 5 shows one embodiment of a coil according to the invention.

Fig. 6 serves to illustrate the method of winding of said coil.

Fig. 7 shows a winding template on which the coil according to the invention may be wound and Fig. 8 shows a second embodiment of a coil according to the invention.

tates Patent" 0 2,930,014 Patented Mar. 22, 1960 Fig. 1 is a side view of a winding device comprising a winding shaft 21 having a cylindrical portion 23 of larger diameter which serves as a winding mandrel. The winding mandrel'23, together with a fixed flange 25 and a flange 27 which can axially move over the winding mandrel, constitutes a winding templet on which some turns of insulated wire of circular cross-section are wound. The beginning 29 of the wire has been passed through an inclined duct 31 extending through the fixed flange 35 and the outlet of which on the inner side of flange 25 adjoins the surface of the winding mandrel 23.

The winding mandrel is rotated in the direction indicated by arrow 33, the winding wire 35 being guided in the axial direction by a winding finger (not shown) in such manner that the wire invariably remains substantially parallel to the flange 25 and the first turn (numbered 1) comes to lie closely along the flange 25 and hence in a flat plane at right angles to the winding shaft 21. At the area at which the wire enters the winding templet, at the end of the first turn the wire is moved on in the axial direction through a distance equal to the diameter d of the wire, resulting in an inclined, turn transition portion 1' which is thus not located in the above-mentioned plane. The subsequent turns 2, 3, 4, 5 which, together with turn 1, constitute the first winding layer extend similarly.

The flange 27 is fixed, for example by means of a screw 37, in a position in which the distance between the flange and the last turn 5 of the first winding layer equals half the wire thickness As may be seen from Fig. 1, when the wire is wound further, the wire leaves the level of the first layer and passes to the level of the second layer (turn 6) at the area of the axial staggering of the turns (in Fig. 1 approximately at the level of the centre line of the winding mandrel). This portion of the wire connecting the two, adjacent layers, known also as a transition or transition portion, may also clearly be seen in Fig. 2, which is an axial view in the direction of the arrow 39 of a coil with four layers wound on the mandrel. The turns of the second layer--and of all subsequent layers-are each likewise located substantially in a flat plane at right angles to the winding shaft, which is facilitated due to each turn being accommodated in a groove formed by every two adjacent turns of the preceding layer (see also Fig. 3, which is an axial section of the coil shown in Fig. 2).

In Fig. l, the inclined turn transition portions 1', 2', etc. with respect to the perpendicular winding portions 1, 2, etc. of the first layer are shown with sharp bends (the transitions are actually bent in a continuous way) in order toillustrate that the points of transition (bending points) are located on parallel lines A1, B and A B respectively, which are inclined with respect to the winding shaft. Assuming that the turns completely ongage one another and cannot be compressed, it will readily be recognized that the angle ,8 enclosed, for example,

by the line A B and the flange 25 is equal to ness) to turn 11 (layer 3) is displaced tangentially in the'same direction (points C and C etc'. Fig. 2 clearly crease in diameter of the turns) occurs at the transitions (for example 6') in the second layer and the subsequent layers, since each turn at these transitions must step over two underlying inclined wire portions. This is an additional reason forthe tangential displacement of the transitions of the turns; they seek so-to-s'ay a place beside the ridge, where the underlayer is less high than on the ridge itself. V

Fig. 4 shows the appearance of a coil thus wound-in the case under consideration a coil having a rectangular aperture-as viewed on one of the two end surfaces (flanks). The figure clearly shows the line (or Zone) 41, on which in this end surface the transitions between every two sequential layers are located. The angle enclosed by the transitions between every two turns of.

one layer (turn transitions, for example 1 in Fig. 1) and the end surface is actually much smaller than in Fig. 1;, especially in the. first layers of a rectangular coil, so that the transitions between'the layers (layer transitions) initially are substantially not shifted tangentially. -The displacement occurs after about or more layers, which is attributable to the fact that the initially flat layers now acquire a slightly curved shape on the side of the rectangular coil, on which the transitions cross one another.

If no particular steps are taken, the layer transitions ultimately come to lie-in practice mostly already after a comparatively small number of layers-in the vicinity of one of the diagonals or corners of the coil, that is to say diagonal 43 and this has-been found to be destructive of the regularity of the winding. Since the layer transitions-naturally the most critical portions of the coil as far as winding is concerned'now must be produced in a region in which the curvature of the layers greatly varies, to wit, at the area of the diagonal, the regularity of winding is disturbed, thus rendering regular winding further impossible. Rectangular (in general polygonal) coils can thus be wound in the described manner with only few turns and layers. Disturbances may occur already with 10 layers or less, more particularly if the winding process is effected at a comparatively high speed, for example 1000 and more rev/min.

According to the invention, said disadvantage is obviated by a structure of the coil, an example of which is shown in Fig. 5. This figure shows that the line 45 of the layer transitions exhibits an acute bend, so that the whole line extends within the side or sector of the coil located between two sequential half diagonals 43 and 47 and hence in the safe region. If necessary, the line 45 may exhibit more than one bend (see Fig. 8).

It will now be explained with reference to Fig. 6, which shows a winding device similar to that of Fig. 1, in what manner the variation in direction of the line 45 may be achieved. The difference with respect to Fig. 1 is that the turns in this case do not engage one another. However, the transition portions 1', 2 etc. engage one another. This situation may be obtained, for example, by guiding the winding wire by means of a winding finger, which is moved to and fro at a speed a little higher than would correspond with the winding of engaging turns. Fig. 6 clearly shows that the turn transitions in this case are displaced in a direction opposite to that of Fig. l.'

Consequently, the essential point is to influence the conditions of winding. after a certain (non-critical) number of layers has been wound, in such manner that the situation shown in Fig. 1 changes to that shown in Fig. 6 (or conversely), that is to say in such manner that the turns initially engage one another and after some time do not engage one another. The spacing between the turns need be very small only (for example a'few percent of the wire diameter d) since, as mentioned before,

the angle a is actually very small, for example, only one degree or less.

It has been found in practice that the said change of situation may readily be achieved and has the character of an abrupt change, resulting in the bend shown in Fig. 5. In order to bring about said change, it suffices, for example, either slightly to reduce the diameter of the wire, for example by increasing the tensile stress during winding, or to arrange for the wire 35 to extend between two pressure rollers with axes at right angles to the winding shaft. When the tensile stress is decreased again or the pressure rollers are caused to disengage from the wire, the line 45 again acquires the initial direction and a second bend results.

Another possibility is, for example, the use of a winding mandrel as shown in Fig. 7, in which the space b between the flanges above a determined distance to the winding shaft is slightly greater (an amount Ab, for example about 10% of the diameter of the wire) than in the part of the winding space to be wound first. The

change of the winding situation takes place after some layers have already been wound in the wider portion. This is a result of the fact that each turn is accommodated in a groove formed between the adjacent turns or change a winding situationwhereby the transitions abruptly come to lie on the other side of the ridge (elevation of the underlayer).

It is alternatively possible for the winding space between the mandrel flanges to be widened in the'sector bounded approximately by a half centre line (49 in Fig. 5) and the half diagonal (43) which follows in the initial direction of the line 45. The layer transitions are initially located substantially outside this 'sector and are not afiected by the widening of the winding space. However, as soon as the transitions come to lie wholly or substantially within the sector of greater width, bending of the line 45 soon occurs.

Still another posibility is provided by the use of a pressure member known per se, for example of highly flexible leather, having a width equal to that of the winding space (which in this case does not require a widened portion). Said member during winding bears at slight radial pressure upon the coil through the whole width thereof at the area at which the wire reaches the coil, invariably pushing so-to-say the wire in position beside the preceding turn. The pressure exerted upon the wire by the piece of flexible leather obviously has an axial component, more particularly at the transitions (1', 2', etc.), which slightly compresses the wires. The situation shown in Fig. 6 may be brought about by considerably increasing at a given moment the pressure exerted by the piece of leather.

All these methods come to this; that the ratio between wire thickness and width of the winding space is varied at least locally during winding.

It has been found possible in the described manner to wind rectangular coils having, for example, layers each of 100 turns of wire of 0.1 mm. at a comparatively high speed, for example, 1000 rev./min. and with a low percentage of loss. 7

The side of the coil on which the transitions are located (the upper side in Fig. 8) is naturally thicker in the radial direction than the other sides. In the coil according to the invention, such is the case only with one of the sides, or, with a slightly diflerent winding method, with two opposite sides, but at any rate not with two adjoining 'or adjacent sides and hence, for

example, not with the upper side and the side 51 in.

not true, two opposite sides 51 and 53 of the coil may be wound with a large space factor and minimum thickness, which is important when the coil is used in combination with a shelltype core (55, shown in dotted line in Fig. 8) which comprises, for example, E-shaped and I-shaped stacked laminations.

What is claimed is:

1. A polygonal coil having a large space factor and a plurality of sides and two end surfaces, comprising a plurality of wire layers each composed of a plurality of wire turns, each of said turns lying substantially in at least one plane at right angles to the axis of the coil, the wire transitions connecting together adjacent layers being located only along predetermined non-adjacent sides of the coil and said transitions between layers forming a line extending from the inside layer to the outside layer along the coil end surfaces, said line bending in one direction over part of its length and bending in the opposite direction over another part of its length.

2. A polygonal coil as claimed in claim 1 wherein said wire transitions between layers are all located along one side only of the coil and are thus confined between adjacent half-diagonals.

3. A machine-wound multi-sided polygonal coil having a large space factor and two end surfaces, comprising a plurality of abutting wire layers each composed of a plurality of wire turns, each of said turns lying substantially in a plane at right angles to the axis of the coil, the wire transitions connecting together adjacent layers being located only along one side of the coil and being confined between adjacent half-diagonals, whereby only said one side has a larger thickness than the remaining sides, and said transitions between layers forming a line extending from the inside layer to the outside layer along the coil end surfaces, said line bending in one direction over part of its length and bending in the opposite direction over a further part of its length and bending back in said one direction over still a further part of its length.

4. A polygonal coil as claimed in claim 3 wherein said coil is rectangular, the turns of some layers completely engage one another, but the turns of other layers are slightly spaced from one another.

-5. A coil as claimed in claim 3 wherein some of the turns of the coil are slightly spaced from one another, and the transition wire portions between adjacent turns in a layer are in engagement with one another.

References Cited in the file of this patent UNITED STATES PATENTS 535,105 Heath Mar. 5, 1895 1,956,826 Engholm May 1, 1934 1,981,066 Osno's Nov. 20, 1934 2,060,856 DeBell Nov. 17, 1936 2,426,090 Gartner Aug. 19, 1947 2,455,355 Combs Dec. 7, 1948 2,559,824 Leland July 10, 1951 FOREIGN PATENTS 822,289 France Dec. 24, 1937 

